A conventional example of the aforementioned type of a container with a lid is shown in FIG. 12. FIG. 12(A) is a plan view, and FIG. 12(B) is a sagittal cross section taken along V-V of FIG. 12(A). A container 100 with a lid shown is a container generally referred to as a sample tube with a height of about 4 cm and a diameter of about 1 cm. It is used for the storage, mixture, centrifugation or the like of a sample or the like in biology laboratories, for example. It includes a container portion 10 with an opening portion 11 for the loading and unloading of a content such as a sample, and a lid portion 20 that can be detachably fitted with the opening portion 11 (upper-end portion of container portion 10) so as to close the same.
More specifically, the container portion 10 is cylindrical in shape in the upper portion thereof. Its lower portion, which is not shown, is conically shaped, as shown in FIG. 1(B). The container portion 10 is either transparent or semi-transparent. Along the outer periphery of the container portion 10 near the upper end thereof, a flange portion 15 is integrally provided for reinforcement and for functioning as a lid receiver. The flange portion 15 and the lid portion 20 are coupled by means of a flexible sheet hinge portion 25.
The lid portion 20 includes a lid-body portion 21 with an inverted-U cross section that is externally fitted with an upper-end portion (opening portion 11) of the container 10. It also includes an internally fit portion 22 with a short-cylinder shape that is hermetically and internally fitted with the upper end portion (opening portion 11) of the container 10. It is also provided with a protruding nail portion 27 protruding from the lid-body portion 21 outwardly in the radial direction (in the plane of the opening of the container portion 10 and beyond the flange portion 15), thus providing a finger rest for opening the lid portion 20.
The container portion 10, the flange portion 15, the hinge portion 25, and the lid portion 20, of which the container with a lid 100 is composed, are all formed of the same synthetic resin material.
In the thus-structured container with a lid 100, when opening the lid portion 20 from the closed state shown in (B), the protruding nail portion 27 is pushed or pulled up with a finger, whereby the lid portion 20 can be opened as shown in (C). Conversely, when closing it from the open state (C), the lid portion 20 is placed on the opening portion 11 of the container portion 10 and pushed down. As a result, as shown in (B), the internally fit portion 22 is pressed within the internal periphery of the opening portion 11, whereby the opening portion 11 is hermetically closed.
Although large force must be initially applied when opening the lid portion 20, the lid can be fully opened easily once it is even slightly moved in the opening direction.
However, in the conventional container with a lid (sample tube) 100, once a sample or the like is put in the container portion and stored as frozen or refrigerated with the lid portion closed, it has often been difficult to open the lid portion so as to use the stored sample for experiment or measurement, for example, when the lid portion is very tightly closed.
If the lid portion cannot be easily opened, a tremendous amount of time and energy would have to be spent for opening and closing the lid portion if hundreds of sample tubes are involved. That would hinder the necessary experiment or measurement, and could possibly hurt the fingers due to the large burden placed on them.
Further, when the sample needs to be sucked out with a pipette, for example, if the lid portion is too tightly closed, it would be impossible to open the lid portion with a single hand. As a result, it would be necessary, for example, to once place the pipette held in the right hand on the experiment table or the like, hold the sample tube with the left hand, and then open the lid portion, with some difficulty, with the right hand. This would result in a greatly reduced efficiency and a longer time for the pipetting of the sample. Even if the time loss per single instance of opening or closing is small, the total time loss cannot be ignored when the lid portion needs to be opened or closed thousands or tens of thousands of times.
On the other hand, in the conventional sample tube, the lid portion supposed to be tightly closed could inadvertently be opened. Specifically, sometimes it is necessary to heat the sample tube containing a sample when subjecting the sample to an experiment or measurement. In such a case, the portion of the sample tube below its upper portion (lid portion) is submerged in a hot water bath so as to heat the sample in a cyclic movement, when the pressure inside the sample tube could increase so much that the lid portion is opened. If that happens, splashes of the hot water, the surface of which is agitated by the cyclic movement in the sample tube, could jump into the sample tube, thereby completely ruining the sample.
In order to prevent such a problem, conventionally the lid portion is locked by means of a separate clip or the like that is attached between the lid portion and the container portion, thereby preventing the accidental opening of the lid portion. However, when the lid portion is locked by a separate clip or the like, the clip or the like needs to be locked and unlocked for opening and closing the lid portion, which is troublesome and time-wasting.
It is therefore an object of the invention to solve the aforementioned problems and to provide a container with a lid in which the lid portion can be easily opened with one hand without placing too much burden on the fingers even if it is tightly closed, and which container has a relatively simple structure and can be manufactured at low cost.
Another object of the invention is to provide a container with a lid that can be locked so that the lid portion does not open inadvertently due to the increase in the internal pressure, for example, in which the locking and unlocking operations can be very simply carried out, and which has a relatively simple structure and can be manufactured at low cost.
It is yet another object of the invention to provide a container with a lid whereby the aforementioned two objects can be achieved simultaneously and reasonably.